Inactive data is data that does not "show up" in your file tree, also known as your directory or data structure. Even though this data resides on your hard drive, it cannot be accessed by the operating system and it therefore it can no longer be maintained by it. Deleted data or data existing prior to a disk reformat operation are two examples, but there are other types as well. In essence, data which for any cause you no longer have access to or cannot view (i.e., does not appear anywhere on your drive), but still resides somewhere on your hard drive, is classified as inactive data.

Conversely, active data, by virtue of being maintained by the operating system, retains its file integrity; you can think of this as a sort of shield that protects all the file components from unintended corruption or damage which would result from normal system activities were the shield not in place. This type of damage is referred to as logical corruption.

While file integrity is being maintained for any particular file, all of the several components of the file, such as the details about that file (e.g., name, size, creation date, etc.), as well as all the content information held within it, are "known" to your system and available for your access and use. When data is inactive it has no "protection" and is then subject to irreparable, unrecoverable damage by means of one, or possibly all of its components becoming overwritten with new active data belonging to some process or application which is irrelevant to the file being corrupted.